1124 DOI: 10.17344/acsi.2020.5963 Acta Chim. Slov. 2020, 67, 1124–1138 Scientific paper GO/PAMAM as a High Capacity Adsorbent for Removal of Alizarin Red S: Selective Separation of Dyes Mohammad Rafi,1 Babak Samiey1,* and Chil-Hung Cheng2 1 Department of Chemistry, Faculty of Science, Lorestan University, Khoramabad 68137–17133, Lorestan, Iran 2 Department of Chemical Engineering, Ryerson University, M5B 2K3, Toronto, Ontario, Canada * Corresponding author: E-mail: [email protected] , [email protected] Received: 03-16-2020 Abstract Adsorption of Alizarin Red S (ARS) on graphene oxide/poly(amidoamine) (GO/PAMAM) was studied at different ARS initial concentrations, temperatures, pHs, shaking rates and contact times. Adsorption sites of GO/PAMAM were phe- + + nolic –OH (Ph) group of GO and amine groups (–NH2, –NH 3 and –NHR 2) of PAMAM dendrimer moieties of GO/ –1 PAMAM. At pH = 2 and 318 K, maximum adsorption capacity (qe,max) of the adsorbent was 1275.2 mg g which is one of the highest capacity in the literature. Thus, GO/PAMAM in this work acted as a superadsorbent for ARS. At the – incipient of adsorption, ARS molecules were adsorbed on Ph sites that was reaction-controlled step, (Ea = 114.5 kJ mol–1). Adsorption of ARS–on the remaining sites was diffusion–controlled. In alkaline media, two other types of ARS + molecules were identified during that were adsorbed on Ph and –NH 3 sites. Further increasing the pH of the solution, decreased the number these two sites and yielded a reduced adsorption capacity (qe,max). Methylene blue (MB), thionine (Th), pyronin Y (PY), acridine orange (AO), methyl blue (MEB) and janus green (JG) dyes were selectively separated from their mixtures with ARS molecules using GO/PAMAM at pH of 2. The used adsorbent was recycled efficiently by using ethylenediamine very fast. Keywords Alizarin Red S; GO/PAMAM; Adsorption; ARIAN model; KASRA model; ISO equation 1. Introduction as a chromogenic agent for selective spectroscopic deter- mination of some compounds.11 Wastewater generated by different industries con- For removing ARS from wastewaters, various kinds tains pollutant compounds that are hazardous to the health of adsorbents were used, such as activated carbon/γ-Fe2O3 of human beings and animals. Dye compounds included nano-composite,12 modified nano-sized silica,13 magnetic in these pollutants of wastewater are produced by indus- chitosan,14 lantana camara,15 coconut shell activated car- 16 17 tries like food, paper, rubber, textile, printing, tanning, bon, activated clay modified by iron oxide, Fe3O4/CeO2 dyestuff and pigment industries. During the last decades nanocomposite,18 calcined [Mg/Al, Zn/Al and MgZn/Al]- 19 20 extensive progress has been made for treatment of indus- LDH, nanocrystalline Cu0.5Zn0.5Ce3O5, activated car- 21 trial wastewaters. A number of techniques used for this bon engrafted with Ag nanoparticles, nano-Fe3O4 and purpose are filtration,1 chemical oxidation,2 ion exchange,3 corn cover composite22 and chitosan/ZnO nanorod com- 4 5 6 23 biological degradation, reverse osmosis, coagulation, posite. The qe,max value values of these adsorbents are and adsorption.7 Adsorption is a facile, cost effective and tabulated in Table 1. widely-applied method to remove dye compounds from In this study, graphene oxide/poly(amidoamine) wastewater systems and in many cases can be recycled eas- (GO/PAMAM) was synthesized by grafting poly(ami- ily. doamine) (PAMAM) dendrimer to graphene oxide.24–26 Alizarin Red S (ARS), sodium 3,4-dihydroxy-9,10-di- The as-synthesized GO/PAMAM and ARS–ad- oxo-9,10-dihydroanthracene-2-sulfonate, is also known as sorbed GO/PAMAM were characterized by different tech- Mordant Red 3 or Alizarin Carmine which is an anth- niques like BET (Brunauer-Emmett-Teller), SEM (Scan- raquinone and anionic dye. ARS is applied as an acid-base ning Electron Microscope), EDS (Energy Dispersive indicator,8 a red textile dye,9 for staining in histology10 and X-Ray Spectroscopy), XRD (X-Ray Diffraction) and FTIR Rafi et al.: GO/PAMAM as a High Capacity Adsorbent for Removal ... Acta Chim. Slov. 2020, 67, 1124–1138 1125 Table 1. Maximum adsorption capacity (qe,max) of ARS on a series of adsorbents. –1 Adsorbent T (K) qe,max (mg g ) Ref. Activated carbon/γ-Fe2O3 298 108.7 12 Modified nano-sized silica 293 200.0 13 Magnetic chitosan 303 40.1 14 Activated clay modified by iron oxide 298 32.7 17 Fe3O4/CeO2 nanocomposite 303 90.5 18 Activated carbon engrafted with Ag nanoparticles 298 232.6 21 Nano-Fe3O4 and corn cover composite 298 10.4 22 GO/PAMAM 328 1275.2 This work (Fourier Transform Infrared Spectroscopy) techniques. rics-tristar 3020 instrument, Figure S1. The obtained BET The adsorption process of ARS on GO/PAMAM surface isotherm for GO/PAMAM was type IV and its BET sur- was carried out under different experimental conditions face area, maximum pore volume (slit pore geometry), ad- including ARS concentration, ionic strength, pH, temper- sorption average pore diameter (by BET) and pore volume ature, shaking rate and contact time. Due to high adsorp- were 9.59 m2 g–1, 0.0044 cm3 g–1, 18.9 nm and 0.045 cm3 tion capacity of GO/PAMAM for ARS, GO/PAMAM was g–1, respectively. It is noticeable that BET surface and pore considered as a superadsorbent for ARS dye, Table 1. volume of GO/PAMAM in this work are several times Kinetics and thermodynamics of adsorption of ARS higher than those of reported.26 Also, its hysteresis loop on GO/PAMAM surface were investigated using the ARI- was H3 which in this case aggregates of platelike GO/ AN and KASRA models respectively that elucidated the PAMAM nanoparticles form slit-like pores.27 process mechanism. Also, high capacity adsorption of GO/ Scanning electron micrographs (SEM) of GO/ PAMAM in acidic pHs for ARS was used for selective sep- PAMAM and ARS-adsorbed GO/PAMAM samples at pHs aration of a number of dyes from their mixtures with ARS. of 0, 2 and 13 were taken using a MIRA3 TESCAN equip- ment at 15 keV. The SEM photos of pristine GO/PAMAM and its samples obtained under different conditions exhibit- 2 Experimental ed similar surface morphology which were aggregations of PAMAM-covered particles with a porous morphology, Fig- 2. 1. Chemicals ures 1(a)–1(h). The average size of GO/PAMAM particles Alizarin Red S, alizarin, methylene blue, acridine or- estimated by SEM technique was about 30 nm, Figure S2. ange, thionine, pyronin Y, methyl blue, janus green B, so- EDS spectrum of the as-synthesized GO/PAMAM dium hydroxide, sodium chloride, sodium nitrate, potassi- was acquired by a MIRA3 TESCAN equipment. Accord- um permanganate, concentrated sulfuric acid (98%), ing to the results of EDS, the atomic percentages of ele- hydrochloric acid (37%), hydrogen peroxide (30%), meth- ments on its surface were similar to the published results26 anol (≥99.9%), ethanol (≥99.9%), ethylenediamine which confirmed the formation of GO/PAMAM, Figure (≥99%), diethylenetriamine (≥98%), methyl acrylate S3. The XRD pattern of as-synthesized GO/PAMAM was (≥99%), N,N-dimethylformamide (DMF) (≥99.8%), tet- recorded by a Rigaku D-max C III, X-ray diffractometer rahydrofuran (THF) (≥99%), acetone (99.8 %), benzene using Ni-filtered Cu-Kα radiation (λ = 1.5406 Å). The (>99%), dimethylsulfoxide (DMSO) (≥99.9%) and diethyl smooth intensity with broad peaks at around 2θ of 26.7° ether (≥99.7%) were purchased from Merck. Graphite showed that the main structure of GO/PAMAM was powder (<20 μm) (≥99.9%) was purchased from Sig- amorphous, Figure 2(a). The XRD spectrum of GO/ ma-Aldrich. All chemicals were used without further puri- PAMAM was similar to that in the literature.26 fication. Also, the FTIR spectrum of GO/PAMAM was taken by a Nicolet IR 100 (Thermo Scientific) FTIR spectropho- 2. 2. Synthesis of GO/PAMAM tometer using KBr pellet technique, Figure 3(a). The peak at 1185 cm–1 was assigned to the stretching vibration of Generation 2 PAMAM (G2 PAMAM) dendrimer C–OH (phenolic) groups of GO/PAMAM.26,28,29 The spec- (the first generation in this kind of nomenclature is called trum was very similar to that of the previous report for G–0.5), graphene oxide (GO) and GO/PAMAM were syn- GO/PAMAM.26 The absence of the peak at 1680–1760 thesized based on the published procedure.26 cm–1 confirmed the lack of carboxylic acid group in GO/ PAMAM. Diminishing the C=O band of GO at 1731cm–1 –1 2. 3. Characterization of GO/PAMAM and the appearance bands at 1637 cm (C=O amide I stretching vibration mode),24,29,30 in the IR spectrum of The nitrogen-based BET specific surface area of GO/ as-synthesized GO/PAMAM confirmed that the GO/ PAMAM was determined by a Pore Size Micromet- PAMAM was synthesized. Rafi et al.: GO/PAMAM as a High Capacity Adsorbent for Removal ... 1126 Acta Chim. Slov. 2020, 67, 1124–1138 Figure 1. SEM images of (a,b) pristine GO/PAMAM, (c,d) GO/PAMAM modified at pH = 0 and ARS-adsorbed GO/PAMAM samples at (e,f) pH = 2 and (g,h) pH = 13. a) b) Figure 3. IR spectra of (a) pristine GO/PAMAM, (b) GO/PAMAM Figure 2. XRD spectra of (a) pristine GO/PAMAM, (b) GO/PAMAM modified at pH = 0 and ARS–adsorbed GO/PAMAM at (c) pH = 0, modified at pH = 0. (d) pH = 2, (e) pH = 5 and (f) pH = 10. Rafi et al.: GO/PAMAM as a High Capacity Adsorbent for Removal ... Acta Chim. Slov. 2020, 67, 1124–1138 1127 Chemical analysis of pristine GO/PAMAM by a ECS As published,29,42 protonated primary amine (– + 4010 CHNS–O elemental analyzer showed that this com- NH 3), phenolic –OH and protonated tertiary amine (– + pound contains 17.22% nitrogen, 64.02% carbon and NHR 2) groups of GO/PAMAM started to be deprotonat- 4.39% hydrogen by mass, Figure S4.